I. Technical Field
The present invention relates to an exhaust turbo supercharger to be used in an internal combustion engine that serves as a power source in a vessel, motor vehicle or power generator, in particular, to a VG (variable geometry) type exhaust turbo supercharger.
II. Description of the Related Art
An exhaust turbo supercharger improves the combustion efficiency of an internal combustion engine by forcefully supplying air into a combustion chamber of the internal combustion engine to improve the output of the internal combustion engine and improve the properties of exhaust gas of the internal combustion engine.
As such an exhaust turbo supercharger, a variable displacement type exhaust turbo supercharger disclosed in Japanese Unexamined Patent Application, Publication No. 2004-156592 is known for example.
This variable displacement type exhaust turbo supercharger has a turbine housing (turbine casing), inside of which there is formed a spiral flow passage, and a turbine wheel provided substantially in the center in the radial direction of this turbine housing. Exhaust gas from an internal combustion engine is supplied into the spiral flow passage of the turbine housing. The turbine wheel is rotably driven by exhaust gas supplied into this spiral flow passage.
Moreover, this variable displacement type exhaust turbo supercharger has a compressor housing, inside of which there is formed a spiral flow passage, and a compressor wheel provided in a substantially radial direction center of the compressor housing. The compressor wheel is rotably driven to take outside air into the compressor housing and deliver the outside air that has been taken in into the spiral flow passage in the compressor housing. The spiral flow passage of the compressor is connected to an air intake system of the internal combustion engine. Accordingly, the outside air that has been delivered into this spiral flow passage by the compressor wheel is forcefully delivered to the air intake system of the internal combustion engine.
The turbine wheel and the compressor wheel are linked by a turbine shaft. A bearing housing is provided between the turbine housing and the compressor housing. In the bearing housing, there is provided a bearing that supports the turbine shaft, allowing it to rotate around the axis.
In the bearing housing, on the outer circumference section of an end to be connected with the turbine housing, there is provided a flange section. In the turbine housing, on an end to be connected with the bearing housing, there is formed a plurality of screw holes on the outside of the area that receives the flange section of the bearing housing. The bearing housing and the turbine housing are connected by engaging a bolt in each of the screw holes provided in the turbine housing. Specifically, the bearing housing is fixed on the turbine housing by the flange section of the bearing housing being pressed against the turbine housing by the head sections of the bolts that engage with each of the screw holes of the turbine housing, or by washers attached to the bolt head sections.
Moreover, between the turbine housing and the bearing housing, there is provided a gasket that prevents exhaust gas that has flowed through an insert section of the turbine shaft between the turbine housing and the bearing housing from leaking to outside of the device. The contact pressure contact pressure of this gasket with the turbine housing and the bearing housing is determined by the fastening force of the bolts.
In this variable displacement type exhaust turbo supercharger, exhaust gas introduced from an exhaust system of the internal combustion engine into the spiral flow passage in the turbine housing rotation-drives the turbine wheel.
As the turbine wheel is rotably driven in this manner, this driving force is transmitted to the compressor wheel via the turbine shaft, and the compressor wheel is thereby rotably driven.
Thus, the compressor wheel takes outside air into the compressor housing and delivers the outside air that has been taken into the spiral flow passage in the compressor housing. As a result, the outside air that has been taken into the compressor housing is forcefully supplied into a combustion chamber of the internal combustion engine.
Furthermore, in this variable displacement type exhaust turbo supercharger, in the turbine housing, there is provided a variable nozzle mechanism for adjusting the displacement of the turbine.
The variable nozzle mechanism has nozzle vanes arranged on the inner circumference side of the spiral flow passage in the turbine housing in a plurality of positions at equal intervals in the circumferential direction of the turbine. Each of the nozzle vanes is provided so as to be able to respectively change the blade angle thereof with respect to a nozzle mount attached to the turbine housing.
The variable nozzle mechanism is to adjust a flow speed of exhaust gas delivered from the spiral flow passage into the turbine housing by adjusting the blade angle of each of the nozzle vanes. In the variable nozzle mechanism, by adjusting the flow speed of exhaust gas delivered to the turbine wheel in this manner, the rotation speed of the turbine wheel is adjusted, and the volume of air delivered to the air intake system by the compressor wheel can be adjusted.